1. Field of the Invention
The invention relates generally to spot welding methods, tools used for spot welding, and parts joined by spot welding.
2. Related Art
Spot welding is oftentimes used to join a first part formed of aluminum to a second part formed of aluminum or another metal material. The parts are held together under pressure by a pair of welding tips, which also function as electrodes. Current is supplied to the welding tips and concentrated in a single spot to melt the surface and form the weld. One drawback of spot welding aluminum parts is that aluminum oxides typically form along the surfaces, which reduces the integrity of the weld.
To break the oxide surface and reduce the amount of aluminum oxides formed during spot welding, the welding tips can present a spherical radius at their terminal end, and rotate continuously or intermittently at a controlled rate as they spot weld the parts together. An example of this technique was developed by KUKA and Mercedes-Benz® and is referred to as robo-spinning. The robo-spinning technique uses a robot to rotate the welding tips and spot weld the parts together. However, due to the significant force applied and the shape of the part being welded, the rotating weld tips tend to move out of position during the spot welding process. In addition, the terminal ends of the rotating welding tips can melt the surfaces of the parts and create locking divots.